The present invention concerns a device for separating immiscible fluids of different specific gravities.
Centrifugal separators are known which are capable of subjecting a stream formed of a mixture of immiscible fluids of different specific gravities to the action of centrifugal forces. The fluid of low specific gravity is essentially collected in the central portion of the final stream, whereas the fluid of higher specific gravity is driven off at the periphery. An annular partition makes it possible to physically separate the two fluids. Such separators are described in the German Pat. No. 1,186,412, the U.S. Pat. No. 3,746,173 and the Swiss Pat. No. 536,126.
In practice, it is not possible to define the precise boundary or limit between the fluids of the final stream, this limit varies, moreover, according to modifications in the relative amounts of the fluids at the inlet of the separator.
However, for certain applications, it is necessary to achieve a complete separation of the fluids so that each of the obtained streams contains only a single fluid.
In the centrifugal separators of the above-indicated type, it is possible to isolate from the final stream, by suitably selecting the diameter of the annular partition, a stream composed of a determined fraction of one single fluid. But the remaining portion of the final stream is constituted of a mixture of fluids which might be treated in a second, serially connected, centrifugal separator. Thus, better separating performances are obtained but, on the other hand, the separation of the fluids is not complete. It is possible, of course, to increase the number of separators, but there is a physical limit forming an obstacle thereto which results from the size to be given to the annular separating partition and moreover, one of the obtained fluids is not completely pure.
In certain separators, the intermediate portion of the stream, located between the central stream and the peripheral stream, is reintroduced at the inlet of the separator. Such separators are described in the article of M. BOHNET entitled "Trennen nicht mischbarer Flussigkeiten" published in "Chemie Ingenieur Technik", vol. 48 No. 3 pages 177-264, and in French Pat. No. 2,130,579.